The First Isolation and Characterization of Free Phenylamidosulfuric Acid and Its Ring-Substituted Derivatives. Postulated Intermediates in the Sulfonation of Aromatic Amines

Abstract

Thirteen free arylamidosulfuric acids were prepared and charactrized for the first time. These acids could readily been obtained in a pure state simply by adding concentrated hydrochloric acid to a cold aqueous solution of the corresponding ammonium salts. These compounds are non-hygroscopic, crystalline solids and quite stable at room temperature under anhydrous conditions. The spectral data clearly showed that all the arylamidosulfuric acids exist as zwitterions, ArNH2+–SO3−, in the solid state.